It is known to detect leakage in a heat exchanger by subjecting the first or the second side of said heat exchanger to pressure followed by a measuring of whether a loss of pressure occurs. However, this method is not reliable as the heat exchanger may have such a small hole that it can maintain the pressure for such a long period of time that it creates a false sense of security.
It is also known under pressure to circulate a liquid admixed an electrolyte on the first side of the heat exchanger, referred to as the donor face, and without pressure to circulate a second liquid on the second side of said heat exchanger, referred to as the recipient face. During the test, it is measured whether the conductance increases on the recipient face as a result of a leakage of donor liquid with electrolyte into the recipient liquid.
It is also known to use the same principle as described above, where the tracer is a colorant or a fluorescent substance, referred to as a fluorofor, instead of being an electrolyte.
The plates in a heat exchanger are pressed into a wave pattern so as both to enlarge the surface of the plates and to cause a turbulence in the liquid flow passing through the heat exchanger. Due to the wavy pattern of the plates, said plates rest on each other in the assembled state of the heat exchanger.
When the donor face is subjected to pressure, which results in a differential pressure, the crests of the wavy patterns are pressed against each other. As a result, a possible leakage located at the crest of the wave pattern is not detected as the compression of the plates presses said plates upwards against each other, thereby closing the leakage, which is not detected accordingly.
In order to solve this problem, many have chosen to pressure test the heat exchanger from both sides. However, such a solution causes a problem when tracers are used. It is necessary to make sure that such tracers, for example electrolytes, colorants or fluorofors, are rinsed completely from the original donor face to prevent a false reaction and consequently a false test result.